An intuitional picture for a QSL with continuous spin rotation symmetry is the Resonating Valence Bond(RVB) state raised by Anderson [1]}. In a RVB picture, the spins form singlet pairs and the ground state is a superposition of all possible pairing configurations, resultantly the lattice rotation and translation symmetries are restored. It was also proposed that when doping charge carriers into the system, the previously paired electrons behaves like Cooper pairs and move coherently. Therefore, the QSL state is driven into a superconductor [1]}. This provides a scheme to explain the mechanism of high-temperature superconductivity in cuprate oxides[3]}. In cuprates, the Neel order is easily destroyed by doped charge carriers. When the doping concentration falls in the optimal region, the cuprate becomes a superconductor with a high critical temperature[4]}, [5]}, [6]}, [7]}, [8]}, [9]}.
